Thermoelectric conversion means to directly convert heat into electricity.  The high conversion efficiency enables to generate electricity using heat waste at ironworks or incinerators.  The development of thermoelectric materials has been an important key for using renewable energy. Thermoelectric materials need to be highly conductive electrically, but not thermally. Rattling vibration of atoms in cages of clathrate compounds has gathered attention as a crucial player to reduce thermal conductivity. Here, rattling was named after "Rattle," a baby toy.

 A research group led by Professor Naoki Toyota at Department of Physics, Tohoku University has successfully photographed the rattling vibration of barium ions in a clathrate (Ba8Ga16Sn30) by terahertz light.  The achievement was produced in collaboration with a research group led by Professor Toshiro Takabatake at Graduate School of Advanced Sciences of Matter, Hiroshima University.  The group of Hiroshima University discovered that the clathrate has a high figure-of-merit for thermoelectric conversion due to the co-existence of low thermal conductivity as in glassy materials and high electrical conductivity as in metals. The paper will be published in “Physical Review Letters” on January 7, 2011 under the title of “Optical conductivity spectral anomalies in the off-center rattling system β-Ba8Ga16Sn30.”

More Information (Japanese)

[Contact]
Professor Naoki Toyota
Department of Physics, Tohoku University
TEL: +81- 22-795-6467　(6604)
E-mail: toyota-n*ldp.phys.tohoku.ac.jp (Replace * with @)

Professor and Director Toshiro Takabatake
Graduate School of Advanced Sciences of Matter, and
Institute for Sustainable Sciences and Development, Hiroshima University
TEL: +81-82-424-7025, FAX: +81-82-424-7029
E-mail: takaba*hiroshima-u.ac.jp (Replace * with @)